Fiberglass insulation is a good electrical insulator, which often results in the insulation generating a static electrical charge during its manufacture, handling, and installation. During these processes friction between glass fibers or between the fibers and other substrates—such as transport conveyors, duct work, packaging materials, or loose-fill blowing equipment—often results in the generation of static charge on the surface of the fibers that does not quickly dissipate. This static charge can cause fibers to adhere to surfaces or become airborne by mutual repulsion, resulting in a reduction of manufacturing efficiency, degradation of air quality, and/or poor installation efficiency.
Bonded glass fiber insulation is manufactured by forming a batt or roll of the glass fibers on a belt. The edges of the batt are trimmed, and the trimmings are ground in a mill and re-used in the manufacturing process. The re-use of the trimmings is known as “re-feed.” Static build-up is not a major concern during formation of the batt/roll, but it can be during the re-feed process.
Non-bonded glass fibers can generate a static charge during both their formation and during their installation (where they are, for example, blown through a tube onto the surface to be treated).
To combat the negative effects from the static charge, antistatic agents (“antistats”) are commonly applied during various stages of manufacturing or product use. Antistats may either limit the generation of static electricity or help dissipate any charges that do form. Most antistats, including the class of quaternary amines, are hydroscopic and attract water vapor from the atmosphere, which helps to dissipate static electricity due to the polar nature of water.
Quaternary amines, however, present a number of challenges to their use in glass insulation. They are ineffective at controlling static at relative humidity levels below about 20% because they cannot attract enough water vapor from the air to sufficiently reduce the static charge. Many quaternary amines have a very high viscosity that makes them difficult to apply and evenly distribute requiring the use of viscosity reducing solvents that add cost and may contribute to flammability and volatility of the mixture. They also may cause skin irritation and corrosion to certain metals. In addition, they may contain volatile components, resulting in gas emissions during the manufacture and use of the insulation, particularly where the temperature of the glass fibers may be elevated. The air emissions must be accounted for during manufacturing, and they can cause a disagreeable odor during the manufacture and use of the insulation.
Many known antistatic agents, and in particular commonly used quaternary amines, are also viscous. Some are nearly solid at room temperature. Their viscosity makes them difficult to apply, which can result in excessive buildup on application equipment and other surfaces during the manufacturing process. One known method for reducing the viscosity of the antistatic agent is to dilute it with a solvent such as water. If a solvent is used in the manufacturing process, however, it must either be dried (complicating the manufacturing process), or it remains in the fibers as residual moisture. This residual moisture can degrade the quality of the glass fibers and further contribute to corrosion of contacted metals.
Glass fibers for use in insulation are very fine and fragile, and are thus prone to break into smaller fibers during handling and installation of the insulation. When breakage occurs, fiber dust/particles are introduced into the air, which can cause physical discomfort (breathing difficulty and eye irritation) to persons handling the insulation. To minimize these effects, glass fiber insulation will typically also include a dedusting agent such as mineral oil, which reduces abrasion and fiber breakage by lubricating the surface of the fiber so that less fiber dust is created. In addition, the dedusting agent is a tacky fluid, which “grabs” the broken fibers, helping to prevent them from being introduced into the air. Dedusting agents contribute to the overall weight and cost of the insulation, however.